1. Field of the Invention
The present invention generally relates a foot rest support member of a motorcycle, such as a scooter. In particular, the present invention relates to a power unit for a motorcycle in which a foot rest support member is secured to an underside of a crankcase.
2. Description of the Related Art
Motorcycles sometimes feature left and right footrests that are secured by a support member to a crankcase of an associated engine. The support member usually has a coupling rod that extends between the foot rests and a mount plate that is welded to an axially intermediate portion of the coupling rod.
The coupling rod passes extends transversely across the vehicle at a location generally below the crankcase. The mount plate faces a central portion of the underside of the crankcase. The crankcase has a plurality of columnar protrusions in a central region of its underside. The protrusions are formed integrally with the crankcase and extend downward from the underside of the crankcase. The mount plate is secured to the lower ends of the protrusions with bolts. An example of such a construction can be found in Japanese Patent Application Hei 9-175,465.
As shown and described in the Japanese reference, the protrusions are located on the rear half of the crankcase. Generally, the rear half of the crankcase houses the gears of a geared transmission. Thus, the rear half of the crankcase typically has a smaller vertical dimension relative to a forward half of the crankcase, which typically contains a crankshaft and an oil pan. In other words, the underside of the rear half of the crankcase is vertically higher above the surface on which the motorcycle is operated than the front half thereof.
As can be appreciated, the mounting position of the engine, in particular the vertical clearance between the engine and the surface on which the motorcycle is operated on, is at least partially determined by a tradeoff between achieving good road clearance and achieving a low center of gravity for the motorcycle. In the prior configurations, the rear half of the crankcase is vertically higher above the road relative to the forward portion of the crankcase. Therefore, the protrusions had to be rather long in order to properly position the footrests relative to the rest of the motorcycle. The length of the protrusions was not desired because the foot rests support the weight of the rider and, therefore, the support member and the protrusions of the crankcase must have a strong and rigid structure to sufficiently support the load from the foot rests. Thus, reinforcement structures would be employed to bolster the strength of the relevant components, which added complication, cost and weight to the final construction.